A simple TCP server

Question

Write a program or function that listens for incoming TCP traffic on port N. It offers a simple service: it calculates sum of IP address fields of incoming connection and returns.

Program or function reads integer N from arguments or stdin. It listens to incoming TCP connections on port N. When someone connects to that port, the program calculates sum of its IP address fields and sends it back to the client with trailing newline and closes connection.

• Port number N is a valid port, and 2¹⁰ < N < 2¹⁵
• Trailing newline can be either \nor \r\n
• You can use either IPv4 or IPv6. Since IPv6 addresses are written in hexadecimal form, you must also provide result in same format, for example 2001:0db8:0000:0042:0000:8a2e:0370:7334 => 12ecd.

This is code-golf. Standard rules and loopholes apply.

Example

You run your server with ./server 1234. The server is now running and waiting for connections on port 1234. Then a client from 127.0.0.1 connects to your server. Your server performs a simple calculation: 127+0+0+1 => 128 and sends the result to the client (with trailing newline): 128\n. Then server closes connection and waits for next client.

Leaderboard

var QUESTION_ID=76379,OVERRIDE_USER=20569;function answersUrl(e){return"https://api.stackexchange.com/2.2/questions/"+QUESTION_ID+"/answers?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+ANSWER_FILTER}function commentUrl(e,s){return"https://api.stackexchange.com/2.2/answers/"+s.join(";")+"/comments?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+COMMENT_FILTER}function getAnswers(){jQuery.ajax({url:answersUrl(answer_page++),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){answers.push.apply(answers,e.items),answers_hash=[],answer_ids=[],e.items.forEach(function(e){e.comments=[];var s=+e.share_link.match(/\d+/);answer_ids.push(s),answers_hash[s]=e}),e.has_more||(more_answers=!1),comment_page=1,getComments()}})}function getComments(){jQuery.ajax({url:commentUrl(comment_page++,answer_ids),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){e.items.forEach(function(e){e.owner.user_id===OVERRIDE_USER&&answers_hash[e.post_id].comments.push(e)}),e.has_more?getComments():more_answers?getAnswers():process()}})}function getAuthorName(e){return e.owner.display_name}function process(){var e=[];answers.forEach(function(s){var r=s.body;s.comments.forEach(function(e){OVERRIDE_REG.test(e.body)&&(r="<h1>"+e.body.replace(OVERRIDE_REG,"")+"</h1>")});var a=r.match(SCORE_REG);a&&e.push({user:getAuthorName(s),size:+a[2],language:a[1],link:s.share_link})}),e.sort(function(e,s){var r=e.size,a=s.size;return r-a});var s={},r=1,a=null,n=1;e.forEach(function(e){e.size!=a&&(n=r),a=e.size,++r;var t=jQuery("#answer-template").html();t=t.replace("{{PLACE}}",n+".").replace("{{NAME}}",e.user).replace("{{LANGUAGE}}",e.language).replace("{{SIZE}}",e.size).replace("{{LINK}}",e.link),t=jQuery(t),jQuery("#answers").append(t);var o=e.language;/<a/.test(o)&&(o=jQuery(o).text()),s[o]=s[o]||{lang:e.language,user:e.user,size:e.size,link:e.link}});var t=[];for(var o in s)s.hasOwnProperty(o)&&t.push(s[o]);t.sort(function(e,s){return e.lang>s.lang?1:e.lang<s.lang?-1:0});for(var c=0;c<t.length;++c){var i=jQuery("#language-template").html(),o=t[c];i=i.replace("{{LANGUAGE}}",o.lang).replace("{{NAME}}",o.user).replace("{{SIZE}}",o.size).replace("{{LINK}}",o.link),i=jQuery(i),jQuery("#languages").append(i)}}var ANSWER_FILTER="!t)IWYnsLAZle2tQ3KqrVveCRJfxcRLe",COMMENT_FILTER="!)Q2B_A2kjfAiU78X(md6BoYk",answers=[],answers_hash,answer_ids,answer_page=1,more_answers=!0,comment_page;getAnswers();var SCORE_REG=/<h\d>\s*([^\n,]*[^\s,]),.*?(\d+)(?=[^\n\d<>]*(?:<(?:s>[^\n<>]*<\/s>|[^\n<>]+>)[^\n\d<>]*)*<\/h\d>)/,OVERRIDE_REG=/^Override\s*header:\s*/i;

body{text-align:left!important}#answer-list,#language-list{padding:10px;width:290px;float:left}table thead{font-weight:700}table td{padding:5px}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b"> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr></thead> <tbody id="answers"> </tbody> </table> </div><div id="language-list"> <h2>Winners by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr></thead> <tbody id="languages"> </tbody> </table> </div><table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table>

Answer 1

Java, 283 275 bytes

Golfed

import java.net.*;class A{public static void main(String[] n)throws Exception{ServerSocket s=new ServerSocket(Integer.valueOf(n[0]));for(;;)try(Socket a=s.accept()){int v=0;for(byte b:a.getInetAddress().getAddress())v+=b&255;a.getOutputStream().write((v+"\n").getBytes());}}}

Ungolfed

import java.net.*;

class A {
public static void main(String[] n) throws Exception {
    ServerSocket s = new ServerSocket(Integer.valueOf(n[0]));
    for (;;)
        try (Socket a = s.accept()) {
            int v = 0;
            for (byte b : a.getInetAddress().getAddress())
                v += b & 255;
            a.getOutputStream().write((v + "\n").getBytes());
        }
}
}

Edit: Down to 274 thanks to @ogregoire

Answer 2

Matlab, 128 139 Bytes

Listens on port n, Ipv4 only (even if it listens on IPv6 too).

function m(n);while 1;t=tcpip('0.0.0.0',n,'NetworkRole','server');fopen(t);fprintf(t,'%d\n',sum(sscanf(t.RemoteHost,'%d.')));fclose(t);end

Answer 3

k (55 characters)

This is essentially a translation of @h.j.k. solution in q with a couple of modifications.

."\\p ",*.z.x
.z.pg:{$+/0x0\:.z.a}
.z.ph:.h.hy[`].z.pg@

Usage: q filename.k PORT

Answer 4

AutoIT, 308 293 281 278 275 274 272 270 264 bytes

Func K($n)
TCPStartup()
$A=TCPListen("127.0.0.1",$n)
Do
$B=TCPAccept($A)
Until $B>0
While 1
$C=TCPRecv($B,$n)
If $C Then
$e=StringInStr($C,"st:")+4
$d=stringsplit(StringMid($C,$e,StringInStr($C,":")-$e),".")
ConsoleWrite($d[1]+$d[2]+$d[3]+$d[4])
EndIf
WEnd
EndFunc

Script-Example.com has an online compiler.

Reusing the port variable ($n) in the TCPRecv max-length parameter. Since it is never going to be less than 1024, it's saving me a byte.

Answer 5

Rust, 185 bytes

use std::{io::*,net::*};|a|while let Ok((mut a,SocketAddr::V6(b)))=TcpListener::bind(("::",a)).unwrap().accept(){write!(a,"{:x}
",b.ip().segments().map(|a|a as _).iter().sum::<u32>());}

This is a closure of type fn(u16). It accepts IPv6 connections and formats its output in hexadecimal. Golfing in Rust can be pretty challenging due to the number of transformations allowed by the compiler. Rust 1.55.0 or higher is necessary to compile this program.

Answer 6

LispyScript, 196 bytes

(->(require"http")(.createServer(function(q r)(r.end((str(-> (r.socket.remoteAddress)(.split".")(.map parseFloat)(.reduce (function(x y)(+ x y)))))'\n')(.listen(get 2 process.argv)"127.0.0.1"))))

If it looks like one of the Node submissions above, that's because it's pretty much just Node with a prettier face.

Ungolfed:

(->
  (require "http")
  (.createServer
    (function (request response)
      (response.writeHead 200 {'Content-Type': 'text/plain'})
      (response.end
        (str (-> (request.socket.remoteAddress)
             (.split ".")
             (.map parseFloat)
             (.reduce (function (x y) (+ x y)))))
          '\n')
  (.listen (|| (get 2 process.argv) 1337) "127.0.0.1"))))

Two functions, two method chains.

Answer 7

Common LIsp (Lispworks), 564 bytes

(require "comm")(defun make-stream-and-talk(handle)(let((stream(make-instance 'comm:socket-stream :socket handle :direction :io :element-type 'base-char)))(mp:process-run-function(format nil "" handle) '() 'f stream)))(defun f(stream)(unwind-protect(progn(multiple-value-bind(address port)(comm:socket-stream-address stream)(declare(ignore port))(format stream "~S"(reduce #'+(mapcar #'parse-integer(split-sequence "."(comm:ip-address-string address)))))(force-output stream))(close stream))))(comm:start-up-server :function 'make-stream-and-talk :service 10246)

ungolfed:

    (require "comm")
    (defun make-stream-and-talk (handle)
      (let ((stream (make-instance 'comm:socket-stream
                                   :socket handle
                                   :direction :io
                                   :element-type
                                   'base-char)))
        (mp:process-run-function (format nil ""
                                         handle)
                                 '()
                                 'f stream)))

    (defun f (stream)
      (unwind-protect
          (progn
            (multiple-value-bind (address port)
                (comm:socket-stream-address stream)
              (declare (ignore port))
              (format stream "~S" 
                      (reduce #'+
                              (mapcar #'parse-integer
                                      (split-sequence "."
                                                      (comm:ip-address-string address)))))
              (force-output stream))
            (close stream))))

    (comm:start-up-server :function 'make-stream-and-talk
                          :service 10246)

Usange:

    c:\~]$ telnet 127.0.0.1 10246


    Connecting to 127.0.0.1:10246...
    Connection established.
    To escape to local shell, press 'Ctrl+Alt+]'.
    you sent: 128
    Connection closed by foreign host.

    Disconnected from remote host(127.0.0.1:10246) at 23:42:56.

    Type `help' to learn how to use Xshell prompt.

Note:

reference Lispworks documents

Answer 8

Object Pascal, 342 340 bytes

A small (well the pascal definition of small...) server with the lowest level Sockets library. Listenes to IP4, port no. on the commandline.

uses sockets;var s,c,l,i,f:integer;a,b:TInetSockAddr;g:string;begin val(ParamStr(1),f,i);s:=fpSocket(2,1,0);a.sin_family:=2;a.sin_port:=ntobe(f);l:=sizeof(a);fpBind(s,@a,l);repeat fpListen(s,1);c:=fpaccept(s,@b,@l);f:=0;for i:=1to 4do f:=f+b.sin_addr.s_bytes[i];Str(f,g);g:=g+#10;fpsend(c,@g[1],length(g),0);fpshutdown(c,2);until False;end.

Ungolfed:

uses
  sockets;
var
  s, c, l, i, f: integer;
  a, b: TInetSockAddr;        { a=server, b=client }
  g: string;
begin
  val(ParamStr(1), f, i);     { store port no. in f }
  s := fpSocket(2, 1, 0);     { 2=AF_INET, 1=SOCK_STREAM, 0=PF_UNSPEC }
  a.sin_family := 2;          { 2=AF_INET }
  a.sin_port := ntobe(f);     { port to listen to, address initialized to localhost by default }
  l := sizeof(a);
  fpBind(s, @a, l);           { bind socket to address:port }
  repeat
    fpListen(s ,1);           { listen for one incoming connection }
    c := fpaccept(s, @b, @l); { accept connection, client address in b }
    f := 0;
    for i:=1 to 4 do
      f := f+b.sin_addr.s_bytes[i]; { add 4 bytes of client address }
    Str(f, g);                      { store f in a string }
    g := g+#10;                     { add newline }
    fpsend(c, @g[1], length(g), 0); { send the addition result }
    fpshutdown(c, 2);               { close the connection }
  until False;
end.

Answer 9

Racket, 174 bytes

(do([l(tcp-listen 1234)])(#f)(let*-values([(i o)(tcp-accept l)][(a b)(tcp-addresses i)])(displayln(for/sum([s(string-split b".")])(string->number s))o)(close-output-port o)))

Ungolfed

(do ([l (tcp-listen 1234)])
    (#f)
  (let*-values ([(i o) (tcp-accept l)]
                [(a b) (tcp-addresses i)])
    (displayln
     (for/sum ([s (string-split b ".")])
       (string->number s))
     o)
    (close-output-port o)))

Shoutout to cat for bringing the Racket competition!

Answer 10

NodeJS, (IPv4 and IPv6) 105 Bytes

require("net").createServer(s=>s.end(eval(s.remoteAddress.replace(/[:.]/g,"+"))).listen(process.argv[2])

Explanation:

require("net")               # TCP library
 .createServer(              # Create the server
   s=>                       # Socket is s
    s.end(                   # Print and end the connection
     eval(                   # Treat the following string like JavaScript
      s.remoteAddress        # The IP address (IPv4 or IPv6, depending on connection)
       .replace(/.|:/g, "+") # Replace all . and : with +
 )))                         # Close server response
 .listen(process.argv[2])    # Listen on the third index of the arg array (["node", "filename.js", "first arg"])